In combines the threshed out, cleaned harvested crop is stored temporarily in a grain tank and is transferred to a transport vehicle by means of an unloading conveyor when a sufficiently high fill has been reached. Since the permissible dimensions of a combine are limited by over the road regulations, grain tanks of larger combines are provided with extension elements that increase the volume of the grain tank during the harvesting process.
Such a grain tank with a ring-shaped extension is described in patent publication no. DE 100 51 096 A. There four elements, of which two are made of flexible material, are pivoted through 90° or more between a flat position and an extended position. U.S. Pat. No. 6,508,705 B proposes a cover arrangement for a grain tank that include two covers connected to each other so as to pivot on two sides of the grain tank. The two other sides of the grain tank extension can be pivoted between a horizontal non-operating position and a vertical operating position. In both publications cited the extension of the grain tank is performed only upward. This has the disadvantage, among others, that the center of gravity of the combine is relatively high when the grain tank is loaded which has the effect of decreasing the steering capabilities during operation around curves and on side slopes. Moreover, the volume of the grain tank extension is limited by its relatively small base surface area.
Patent publication no. DE 1 951 498 A, which is seen as forming a class, describes another combine in which the outer side walls of the grain tank can be pivoted outward to increase the volume of the grain tank during the harvesting process. The upper cover of the additional volume being formed at the sides of the combine is also moved outward so that the grain tank is covered in the upward direction at all times. This leads to the disadvantage that the added supplementary volume remains relatively small.
What is needed is a grain tank for a combine that offers a lower center of gravity and/or a larger additional volume. It is an object of the invention to provide such a grain tank.